Digital broadcast transmission and receiving system having an improved receiving performance and signal processing method thereof

ABSTRACT

A digital broadcast transmitter comprising: a randomizer to receive a data stream of which stuff bytes are inserted into a specified position and to randomize the received data stream; a stuff-byte exchange unit to generate known data having a predefined pattern and to insert the known data into the specified position of the data stream into which the stuff bytes are inserted; an encoder to encode the data stream output from the stuff-byte exchange unit for an error correction; and a modulator and RF converter to modulate the encoded data stream, RF-convert the modulated data stream and transmit the RF-converted data.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit from U.S. patent application Ser. No.11/121,065 filed on May 4, 2005, which claims benefit from U.S.Provisional Application No. 60/568,254 filed on May 6, 2004, in theUnited States Patent and Trademark Office, and Korean Patent ApplicationNo. 2004-101940 filed on Dec. 6, 2004, in the Korean IntellectualProperty Office, the entire contents of which are incorporated herein byreference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present general inventive concept relates to a digital broadcasttransmitting and receiving system and a signal processing methodthereof. More particularly, the present general inventive conceptrelates to a digital broadcast transmitting and receiving system and asignal processing method thereof, which can improve receivingperformance of the system by inserting a known sequence into a VSB(Vestigial Side Band) data stream and transmitting the data stream withthe inserted known sequence.

2. Description of the Related Art

An ATSC (Advanced Television Systems Committee) VSB system that is anAmerican-type digital terrestrial broadcasting system, is a signalcarrier type broadcasting system, and uses a field sync signal in theunit of 312 segments.

FIG. 1 is a block diagram of a transmitter and receiver of an ATSC DTVstandard as a general American-type digital terrestrial broadcastingsystem.

The digital broadcast transmitter of FIG. 1 includes a randomizer 110for randomizing an MPEG-2 (Moving Picture Experts Group) transportstream (TS), an RS (Reed-Solomon) encoder 120 for adding RS parity bytesto the transport stream in order to correct bit errors occurring due tothe channel characteristic in a transport process, an interleaver 130for interleaving the RS-encoded data according to a specified pattern,and a trellis encoder 140 for mapping the interleaved data onto 8-levelsymbols by performing a trellis encoding of the interleaved data at therate of ⅔. The digital broadcast transmitter performs an errorcorrection coding of the MPEG-2 transport stream.

The digital broadcast transmitter further includes a multiplexer 150 forinserting a segment sync signal and a field sync signal into theerror-correction-coded data, and a modulator and RF converter 160 forinserting a pilot tone into the data symbols into which the segment syncsignal and the field sync signal are inserted by inserting a specifiedDC value into the data symbols, performing a VSB modulation of the datasymbols by pulse-shaping the data symbols, and up-converting themodulated data symbols into an RF channel band signal to transmit the RFchannel band signal.

Accordingly, the digital broadcast transmitter randomizes the MPEG-2transport stream, outer-codes the randomized data through the RS encoder120 that is an outer coder, and distributes the coded data through theinterleaver 130. Also, the digital broadcast transmitter inner-codes theinterleaved data in the unit of 12 symbols through the trellis encoder140, performs the mapping of the inner-coded data onto the 8-levelsymbols, inserts the field sync signal and the segment sync signal intothe coded data, performs the VSB modulation of the data, and thenup-converts the modulated data into the RF signal to output the RFsignal.

The digital broadcast receiver of FIG. 1 includes a tuner 210 fordown-converting an RF signal received through a channel into a basebandsignal, a demodulator 220 for performing a sync detection anddemodulation of the converted baseband signal, an equalizer 230 forcompensating for a channel distortion of the demodulated signaloccurring due to a multi-path, a trellis decoder 240 for correctingerrors of the equalized signal and decoding the equalized signal tosymbol data, a deinterleaver 250 for rearranging the data distributed bythe interleaver 130 of the digital broadcast transmitter, an RS decoder260 for correcting errors, and derandomizer 270 for de-randomizing thedata corrected through the RS decoder 260 and outputting an MPEG-2transport stream.

Accordingly, the digital broadcast receiver of FIG. 1 down-converts theRF signal into the baseband signal, demodulates and equalizes theconverted signal, and channel-decodes the demodulated signal to restoreto the original signal.

FIG. 2 illustrates a VSB data frame for use in the American type digitalbroadcasting (8-VSB) system, into which a segment sync signal and afield sync signal are inserted. As shown in FIG. 2, one frame consistsof two fields. One field is composed of one field sync segment that isthe first segment and 312 data segments. The other segment in the VSBdata frame corresponds to one MPEG-2 packet, and is composed of asegment sync signal of four symbols and 828 data symbols.

In FIG. 2, the segment sync signal and the field sync signal are usedfor the synchronization and equalization in the digital broadcastreceiver. That is, the field sync signal and the segment sync signalrefer to known data between the digital broadcast transmitter andreceiver, which is used as a reference signal when the equalization isperformed in the receiver side.

As shown in FIG. 1, the VSB system of the American type digitalterrestrial broadcasting system is a single carrier system, and thus hasa drawback in that it is weak in a multi-path fading channel environmenthaving the Doppler effect. Accordingly, the performance of the receiveris greatly influenced by the performance of the equalizer for removingthe multi-path.

However, according to the existing transport frame as shown in FIG. 2,since the field sync signal that is the reference signal of theequalizer appears once for every 313 segments, its frequency is quitelow with respect to one frame signal and causes the performance ofequalization to deteriorate.

Specifically, it is not easy for the existing equalizer to estimate thechannel using a small amount of data as above and to equalize thereceived signal by removing the multi-path. Accordingly, theconventional digital broadcast receiver has disadvantages that itsreceiving performance deteriorates in an inferior channel environment,and especially in a Doppler facing channel environment.

SUMMARY OF THE INVENTION

The present general inventive concept provides a digital broadcasttransmitting and receiving system and a signal processing methodthereof, which can improve the receiving performance of the system bygenerating and transmitting a transport signal with known data addedthereto in a transmitter side and by detecting the transport signal in areceiver side.

Additional aspects and advantages of the present general inventiveconcept will be set forth in part in the description which follows and,in part, will be obvious from the description, or may be learned bypractice of the general inventive concept.

The foregoing and other aspects of the present general inventive conceptare substantially realized by providing a digital broadcast transmitterwhich comprises a randomizer to receive a data stream of which stuffbytes are inserted into a specified position and randomizing thereceived data stream, a stuff-byte exchange unit to generate known datahaving a predefined pattern and insert the known data into the specifiedposition of the data stream into which the stuff bytes are inserted, anencoder to encode the data stream output from the stuff-byte exchangeunit for an error correction, and a modulator and RF converter tomodulate the encoded data stream, RF-convert the modulated data streamand transmit the RF-converted data.

The data stream may include information about the specified positioninto which the stuff bytes are inserted.

The information may be inserted into a position of the data streampreceding the position into which the stuff bytes are inserted, and mayinclude information about a length of the stuff bytes.

The digital broadcast transmitter may further include a control signalgenerating unit to generate a control signal to control the stuff-byteexchange unit to insert the known data into the position according tothe information.

The encoder may comprise a first RS (Reed-Solomon) encoder to add aparity of specified bytes to the data in order to correct errorsoccurring due to channels, an interleaver to interleave the data towhich the parity is added in a specified pattern, and a trellis encoderto perform a trellis encoding of the interleaved data.

The trellis encoder may have a memory device for a trellis encodingoperation, and can perform a trellis encoding by initializing the memorydevice from the position into which the known data is inserted.

The encoder may further include a packet buffer to receive andtemporarily store the data stream from the first RS encoder.

The packet buffer may receive from the trellis encoder and temporarilystore the known data encoded according to the initialization of thememory device.

The encoder may further include a second RS encoder to generate andoutput a changed parity by performing an RS encoding of the encodedknown data input from the packet buffer to the trellis encoder so as toreplace the parity added by the first RS encoder by the changed parity.

The interleaver can output the known data inserted into the sameposition of a plurality of different data streams output from the firstRS encoder as a successive data stream.

The modulator and RF converter can modulate the data by a vestigial sideband (VSB) modulation method.

The foregoing and other aspects of the present general inventive conceptare also substantially realized by providing a signal processing methodof a digital broadcast transmission, which comprises receiving a datastream of which stuff bytes are inserted into a specified position andrandomizing the received data stream, generating a data stream having aspecified known data and inserting the known data into the position ofthe randomized data stream into which the stuff bytes are inserted,error-correction-encoding the data stream output from a stuff-byteexchange unit, and modulating the error-correction-encoded data stream,RF-converting the modulated data stream and transmitting theRF-converted data stream.

Preferably, the encoding operation may include a first RS (Reed-Solomon)encoding operation of adding a parity of specified bytes to the data inorder to correct errors occurring due to channels, an interleavingoperation of interleaving the data to which the parity is added in aspecified pattern, and a trellis encoding operation of performing atrellis encoding of the interleaved data.

The trellis encoding operation may perform a trellis encoding byinitializing a specified memory device used for a trellis encodingoperation in the position into which the known data is inserted.

The encoding operation may further include the operation of receivingand temporarily storing the data stream generated at the first RSencoding operation, and receiving and updating the known data encodedaccording to the initialization of the memory device.

The encoding operation may further include a second RS encodingoperation of generating a changed parity by re-performing an RS encodingof the encoded known data, replacing the parity added at the first RSencoding operation by the changed parity, and performing a trellisencoding of the known data.

The modulating and RF-converting operation may modulate the data by avestigial side band (VSB) modulation method.

The foregoing and other aspects of the present general inventive conceptare also substantially realized by providing a digital broadcastreceiver comprising a tuner to receive a signal from a digital broadcasttransmitter and to convert the signal to a baseband signal, the signalthat is encoded by inserting known data to a specified position withrespect to a data stream to which stuff bytes are inserted at thespecified position, a demodulator to demodulate the baseband signal, aknown data detector to detect the known data from the demodulatedsignal, and an equalizer to equalize the demodulated signal using thedetected known data.

The known data may comprise a sequence having a predefined pattern.

The known data detector may comprise a symbol number detector to detectinformation about the specified position into which the known data isinserted from the received signal, a segment generator to generate adata frame that includes at least one segment to indicate the positionby an identification sign, an error correction encoder to perform anerror correction encoding of the data frame, and a known symbol outputunit to insert the known data into the position of the encoded dataframe indicated by the identification sign.

The known data detector can output the detected known data to thedemodulator, and the demodulator can perform the demodulation using theknown data.

The foregoing and other aspects of the present general inventive conceptare also substantially realized by providing a signal processing methodof a digital broadcast reception, which comprises receiving a signalfrom a digital broadcast transmitter and converting the signal to abaseband signal, the signal being encoded by inserting known data to aspecified position with respect to a data stream to which stuff bytesare inserted at the specified position, demodulating the basebandsignal, detecting the known data from the demodulated signal, andequalizing the demodulated signal using the detected known data.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the present generalinventive concept will become apparent and more readily appreciated fromthe following description of the embodiments, taken in conjunction withthe accompanying drawings of which:

FIG. 1 is a block diagram of a transmitting and receiving system of ageneral American-type digital broadcasting (ATSC VSB) system;

FIG. 2 is a the structure of an ATSC VSB data frame;

FIG. 3 is a block diagram of a digital broadcast transmitting andreceiving system according to an embodiment of the present generalinventive concept;

FIG. 4 is a structure of a general MPEG-2 transport stream packet;

FIG. 5 is a structure of an MPEG-2 transport stream packet that includesan adaptation field to which stuff bytes are added according to anembodiment of the presentgeneral inventive concept;

FIG. 6 is a data format of an MPEG-2 transport stream packet input to arandomizer according to an embodiment of the presentgeneral inventiveconcept;

FIG. 7 is the data format of a randomized packet according to anembodiment of the presentgeneral inventive concept;

FIG. 8 is the data format of a packet RS-encoded according to anembodiment of the presentgeneral inventive concept;

FIG. 9 is the data format of a packet interleaved according to anembodiment of the presentgeneral inventive concept;

FIG. 10 is the data format of a packet trellis-encoded according to anembodiment of the presentgeneral inventive concept;

FIG. 11 is the data format of a packet to which a parity output from asecond RS encoder is added according to an initialization of a trellisencoder;

FIG. 12 is the construction of a known data detector of a digitalbroadcast receiver according to an embodiment of the presentgeneralinventive concept;

FIGS. 13A and 13B are flowcharts illustrating the operation of a digitalbroadcast transmitter according to an embodiment of the presentgeneralinventive concept; and

FIGS. 14A and 14B are flowcharts illustrating the operation of a digitalbroadcast receiver according to an embodiment of the presentgeneralinventive concept.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Certain embodiments of the present general inventive concept will bedescribed in greater detail with reference to the accompanying drawings.

In the following description, same drawing reference numerals are usedfor the same elements even in different drawings. The matters defined inthe description such as a detailed construction and elements are nothingbut the ones provided to assist in a comprehensive understanding of thegeneral inventive concept. Thus, it is apparent that the present generalinventive concept can be carried out without those defined matters.Also, well-known functions or constructions are not described in detailsince they would obscure the general inventive concept in unnecessarydetail.

FIG. 3 is a block diagram of the construction of a digital broadcasttransmitting and receiving system according to an embodiment of thepresent general inventive concept.

Referring to FIG. 3, the digital broadcast transmitter includes arandomizer 310, a stuff-byte exchange unit 315, a first RS encoder 320,a packet buffer 325, an interleaver 330, a second RS encoder 335, atrellis encoder 340, a multiplexer 350, a modulator and RF converter360, and a control signal generator 370.

The randomizer 310 randomizes an input MPEG-2 transport stream data inorder to heighten the utility of an allocated channel space. The datainput to the randomizer 310 has the data format formed by insertingstuff bytes, which has a specified length of bytes but does not includepayload data, into a specified position of the input transport streamdata, which will be explained in detail.

The stuff-byte exchange unit 315 generates a specified sequence(hereinafter referred to as “known data”) having a specified patternprearranged between a transmitter side and a receiver side. Thestuff-byte exchange unit 315 inserts the generated known data into astuff byte position of the randomized data in replacement of the stuffbytes. The known data can easily be detected from payload data to betransmitted, and thus is used for synchronization and equalizationoperations in the receiver side.

The first RS encoder 320 adds a parity of specified bytes to therandomized data (also referred to as packet data) into which the knowndata is inserted by the stuff-byte exchange unit 315 in replacement ofthe stuff bytes in order to correct errors occurring due to channels.

The interleaver 330 interleaves the packet data to which the parityoutput from the first RS encoder 320 is added in a specified pattern.

The trellis encoder 340 converts the data output from the interleaver330 into data symbols, and performs symbol mapping of the data symbolsthrough a trellis encoding at the rate of ⅔. The trellis encoder 340initializes the value temporarily stored in its own memory device to aspecific value at the start point of the known data. For example, thevalue stored in the memory device can be initialized to a “00.”

The packet buffer 325 extracts and temporarily stores the known datafrom the packet data output from the first RS encoder 320 from the startpoint of the known data. If the known data is trellis-encoded in thetrellis encoder 340 according to the initialization of the memorydevice, the packet buffer 325 receives the known data changed accordingto the initialization of the memory device from the trellis encoder 340,temporarily stores the changed known data in replacement of the previousknown data temporarily stored, and then inputs the changed known data tothe second RS encoder 335 for a parity regeneration.

The second RS encoder 335 replaces the original parity with the newlygenerated parity by receiving the known data changed according to theinitialization of the memory device, and regenerating and inputting thenewly generated parity according to the changed data to the trellisencoder 340. Accordingly, the packet data output from the trellisencoder 340 to the multiplexer 350 represents a data format having theknown data changed according to the initialization of the memory deviceof the trellis encoder 340 and the parity added thereto according to theRS encoding.

The multiplexer 350 inserts a segment sync signal into the data that hasbeen converted into symbols by the trellis encoder 340 in the unit of asegment as shown in the data format of FIG. 2, and inserts a field syncsignal into the data in the unit of a field. In addition, the secondmultiplexer 350 inserts a pilot signal into an edge portion of a lowfrequency band of a frequency spectrum by adding a specified DC value tothe data signal of a specified level.

The modulator and RF converter 360 performs a VSB modulation of thesignal into which the pilot signal has been inserted by performing apulse shaping of the signal and amplitude-modulating the signal with anintermediate frequency (IF) carrier, RF-converts and amplifies themodulated signal, and transmits the converted signal through anallocated channel.

The control signal generator 370 receives the transport stream to whichthe stuff bytes are added, detects information about the position towhich the stuff bytes are added from the transport stream, and generatesand outputs the control signal to recognize the start position and theend position of the known data to the stuff-byte exchange unit 315, theinterleaver 320 and the trellis encoder 340.

The digital broadcast receiver of FIG. 3 includes a tuner 410, ademodulator 420, an equalizer 430, a trellis decoder 440, adeinterleaver 450, an RS decoder 460, a derandomizer 470, and a knowndata detector 480. The digital broadcast receiver operates in a reverseprocess with respect to the digital broadcast transmitter of FIG. 3.

The tuner 410 selects the received signal and converts the selectedreceived signal into a baseband signal.

The demodulator 420 detects the sync signals from the baseband signaland demodulates the baseband signal according to a pilot signal and thesync signals inserted into the baseband signal. The equalizer 430removes a mutual interference between the received data symbols (i.e.,from the trellis encoder 340) by compensating for channel distortion ofthe demodulated signal due to the multi-path of the channel.

The trellis decoder 440 performs an error correction of the datasymbols, decodes the error-corrected data symbols, and outputs decodedsymbol data. The deinterleaver 450 rearranges the decoded data, whichwas distributed by the interleaver 330 of the digital broadcasttransmitter.

The RS decoder 460 corrects errors of the deinterleaved data, and thederandomizer 470 de-randomizes the data corrected through the RS decoder460 so that the data of the MPEG-2 transport stream is restored.

The known data detector 480 detects the position of the known data fromthe demodulated data, and outputs the known data generated by generatingand encoding a segment frame for the demodulator's sync detection andthe equalizer's compensation for the channel distortion.

FIG. 12 illustrates the construction of the known data detector 480 ofthe digital broadcast receiver according to an embodiment of the presentgeneral inventive concept.

Referring to FIG. 12, the known data detector 480 includes a symbolnumber detector 481, a segment generator 483, an encoder 485 and a knowndata output unit 487.

The symbol number detector 481 extracts the information about theposition of the known data from control information bits that includeinformation about the length of an adaptation field of a demodulateddata header part. The information about the position of the known dataincludes the information about the length of the known data. Because theposition of the known data is predetermined, the position and the numberof known symbols according to the encoding of the known data can beobtained from the length of the known data.

The segment generator 483 generates at least one segment to indicate thecorresponding position according to the position and the number of theknown symbols by marking an identification sign that corresponds to thenumber of symbols, and generates the MPEG-2 transport stream thatincludes such a segment.

The encoder 485 encodes the transport frame generated by the segmentgenerator 483 in the same manner as that performed by the transmitterside.

Accordingly, the known data output unit 487 inserts the predefined knowndata into the position of the transport frame encoded by the encoder 485that corresponds to the known symbols obtained according to theidentification sign.

FIG. 4 illustrates the structure of a general MPEG-2 transport streampacket, and FIG. 5 illustrates the structure of an MPEG-2 transportstream packet that includes an adaptation field to which stuff bytes areadded according to an embodiment of the present general inventiveconcept.

Referring to FIG. 4, the general MPEG-2 transport stream is composed ofa TS header part of 4 bytes and an adaptation field or payload data of184 bytes.

Referring to FIG. 5, according to the MPEG-2 transport stream of thepresent general inventive concept, an adaptation field of “n” bytes islocated after the header part of 4 bytes, and payload data of “184-n”bytes is located after the adaptation field. The fifth and sixth bytes,that is, the first two bytes, of the adaptation field constitute controlinformation bits that include length information of the adaptationfield, and stuff bytes according to an embodiment of the present generalinventive concept are inserted into the seventh byte of the transportstream, that is, the third byte of the adaptation field. Accordingly,the transmission rate may be reduced somewhat due to the reduction ofthe payload data as long as the length of the adaptation field intowhich the stuff bytes are inserted. However, the length of theadaptation field is changeable, and thus it can be adjusted in order toimprove the transmission performance.

FIGS. 6 to 11 illustrate data formats that are changed according to thedata processing of an MPEG-2 transport stream packet in a digitalbroadcast transmitter according to an embodiment of the present generalinventive concept. FIG. 13A is a flowchart illustrating the operation ofthe digital broadcast transmitter according to an embodiment of thepresent general inventive concept.

Hereinafter, the operation of the digital broadcast transmitteraccording to an embodiment of the present general inventive concept willbe explained with reference to the accompanying drawings.

The randomizer 310 randomizes an input MPEG-2 transport stream includingstuff bytes of a specified length of bytes (operation S510). The datainput to the randomizer 310 has the data format as shown in FIG. 6.

Referring to FIG. 6, the MPEG-2 packet data includes a header partcomposed of the first byte that represents a sync signal and a PID(Packet Identifier) of three bytes, two-byte control information bitsthat include information about the position of the stuff bytes, andstuff bytes composed of a specified length of bytes. Other bytes of thedata refer to the payload data to be transmitted.

Specifically, the information about the position of the stuff bytes isinserted into the first two control information bits among theadaptation field after the three-byte PID of the header part, and thestuff bytes are inserted into the following adaptation field. Becausethe start position of the stuff bytes is fixed, the information aboutthe position of the bytes is expressed as the information about thelength of the stuff bytes.

Next, the stuff-byte exchange unit 315 generates the known data andinserts the known data into the position of the stuff bytes included inthe data randomized by the randomizer 310 in replacement of the stuffbytes (operation S520). The known data is a specified sequence having aspecified pattern known in advance between the transmitter side and thereceiver side, and can easily be detected distinctively from the payloaddata.

The error correction encoding of the data into which the known dataoutput from the stuff-byte exchange unit 315 is inserted is performed inorder to correct the error occurring due to the channels (operationS530).

FIG. 13B is a flowchart illustrating the error correction encodingprocess.

Referring to FIG. 13B, for the error correction encoding, the first RSencoder 320 performs an RS encoding of the data to add a parity ofspecified bytes to the data (operation S531), the interleaver 330performs a data interleaving of the RS-encoded data in a specifiedpattern (operation S533), and the trellis encoder 340 converts theinterleaved data into data symbols and performs an 8-level symbolmapping of the converted data symbols through a trellis encoding at therate of ⅔ (operation S535). Additionally, the second RS encoder 335regenerates the parity by re-performing the RS encoding using thechanged known data input to the packet buffer 325 (operation S537), andadds the regenerated parity to the data in replacement of the previousparity.

FIGS. 7 to 11 illustrate the structure of the packet data that ischanged according to the error correction encoding process as describedabove.

FIG. 7 illustrates a data stream which is randomized by the randomizer310 and into which the known data is inserted by the stuff-byte exchangeunit 315 in replacement of the stuff bytes. In FIG. 7, the length of theknown data is not indicated, but it can be adjusted according to thechannel environment, the amount, or importance of the data to betransmitted. As this known data is inserted after the randomization asthe data known between the transmitter side and the receiver side, itcan easily be detected in distinction from the randomized payload dataand is used for the synchronization and equalization in the receiverside.

FIG. 8 is a view of the data format output from the first RS encoder320. The first RS encoder 320 adds a parity of specified bytes to thedata output from the stuff-byte exchange unit 315 in order to correctthe errors occurring due to the channels. Referring to FIG. 8, the RSparity of 20 bytes is added to an end part of the data stream of 188bytes output from the first RS encoder 320.

FIG. 9 illustrates the data format output from the interleaver 330. Theinterleaver 330 distributes the data on the time axis so that the orderof the data stream is distributed and the transport signal becomesstrong against the interference.

According to this data distribution performed by the interleaver 330,the data bytes arranged at the same positions of the different segmentsin a vertical direction, as shown in FIG. 8, are rearranged as thesuccessive data stream in a horizontal direction in the unit of 52bytes.

The fourth and fifth bytes of the respective segments, which arecomposed of the control information bits including position informationof the known data in FIG. 8, are changed to the data stream(M56.about.M5 (B3) and M57.about.M6 (B4)) successively in the horizontaldirection as shown in FIG. 9 after the interleaving is performed.Accordingly, the control information bits are successively output.

The known data inserted into the fifth position of the respectivesegments are changed to the data stream (M58.about.M7 (B5), M59.about.M8(B6), . . . , M60.about.M9 (B7)) successive in the horizontal direction,as shown in FIG. 9, after the interleaving is performed. Accordingly,the same bytes of the known data inserted into the respective segmentsare output as the successive stream in the unit of 52 bytes.

FIG. 10 illustrates the data format output from the trellis encoder 340of FIG. 3. The trellis encoder 340 encodes each byte of the data outputfrom the interleaver 330 to four 8-level symbols.

In FIG. 10, the known data appear for every 52 segments, and appear assuccessive symbols for a specified length, for example, 208 symbols. 6known data sequences appear in one field. That is, 10*6=60 known datasequences including 10 stuff bytes appear in one field of the transportstream. Accordingly, the known data sequence can easily be detected fromthe payload data stream according to the length of the known data.

FIG. 11 illustrates the process of changing the parity according to theoperation of the second RS encoder 335. The packet buffer 325 extractsand temporarily stores the known data from the packet output from thefirst RS encoder 320 from the start point of the known data. If theknown data is trellis-encoded in the trellis encoder 340 according tothe initialization, the packet buffer 325 receives the known datachanged according to the initialization from the trellis encoder 340,temporarily stores the changed known data by updating the previous knowndata temporarily stored, and inputs the changed known data to the secondRS encoder 335 for the parity regeneration. The second RS encoder 335generates the new parity (changed) by performing the RS encoding of thechange known data, transmits the new generated parity to the trellisencoder 340 to replace the previous parity with the changed parity, andperforms the trellis encoding of the data symbols to output thesuccessive trellis-encoded symbols.

Accordingly, the packet data output from the trellis encoder 340 to themultiplexer 350 is the data obtained by trellis-encoding the known datachanged according to the initialization of the memory device of thetrellis encoder 340 and the packet data into which the parity is addedaccording the RS encoding of the 8-level symbols.

Next, the multiplexer 350 inserts a segment sync signal into the symboldata in the unit of a segment of the symbol data, inserts a field syncsignal into the symbol data in the unit of a field, and then inserts apilot signal into the frequency spectrum (operation S540).

The modulator and RF converter 360 performs a VSB modulation of thesignal into which the pilot signal is inserted by performing a pulseshaping of the signal and amplitude-modulating the signal with anintermediate frequency (IF) carrier, RF-converts and amplifies themodulated signal, and transmits the converted signal through anallocated channel (operation S550).

FIGS. 14A and 14B are flowcharts illustrating the operation of thedigital broadcast receiver according to an embodiment of the presentgeneral inventive concept.

The tuner 410 selects the received signal and converts the selectedsignal into the baseband signal (operation S610).

The demodulator 420 detects the sync signals from the baseband signaland performs the demodulation of the baseband signal according to thepilot signal and the sync signals inserted into the baseband signal(operation S620).

The known data detector 480 detects the position of the known data fromthe equalized data and outputs the detected known data (operation S630).

The symbol number detector 481 extracts the information about theposition of the known data that includes the length of the known datafrom control information bits that include information about the lengthof an adaptation field of a demodulated data header part (operationS631).

The symbol number detector 481 extracts the information about theposition of the known data from control information bits that includeinformation about the length of an adaptation field of a demodulateddata header part. The information about the position of the known dataincludes the information about the length of the known data. As theposition of the known data is predetermined, the position and the numberof known symbols according to the encoding of the known data can beobtained from the length of the known data.

The segment generator 483 generates at least one segment to indicate thecorresponding position according to the position and the number of theknown symbols by marking an identification sign that corresponds to thenumber of symbols, and generates the MPEG-2 transport stream thatincludes such a segment (operation S633).

The encoder 485 performs the error correction encoding of the transportframe generated by the segment generator 483 in the same manner as thatperformed by the transmitter side (operation S635). The known dataoutput unit 487 inserts the predefined known data into the position ofthe transport frame from the encoder 485 that has the identificationsign to output the transport frame into which the known data is insertedto the equalizer 430 (operation S637).

The equalizer 430 performs the equalization by compensating for thechannel distortion of the demodulated signal and removing the mutualinterference among the received data symbols (operation S640). Theequalizer 430 compensates for the channel distortion using the knowndata output from the known data detector 480. Also, the detected knowndata may be provided for the sync detection of the demodulator 420.

The synchronized and equalized data is error-corrected, and theerror-corrected symbols are decoded. The decoded data is rearrangedthrough the deinterleaving process, and then is error-corrected throughthe RS decoding (operation S650).

The error-corrected data is derandomized, and then output as the MPEG-2transport stream data (operation S660).

As described above, according to an embodiment of the present generalinventive concept, the receiving performance of the digital broadcastreceiver, such as the synchronization and the equalization can beimproved even in a inferior multi-path channel by generating andinserting the stuff bytes into the MPEG-2 transport stream, andtransmitting the transport stream into which known data is inserted inreplacement of the stuff bytes in the digital broadcast transmitter, andby detecting the known data from the received signal and using the knowndata for the synchronization and the equalization in the digitalbroadcast receiver.

According to an embodiment of the present general inventive concept, theoperation performance of the equalizer can be improved through theproper adjustment of the amount and the pattern of the sequence of theknown data inserted into the transport stream, and thus the receivingperformance of the digital broadcast receiver can be improved.

Furthermore, the performance of the equalizer and the digital broadcastreceiving performance can be enhanced by adjusting the sequence of theknown data by a proper amount for the synchronization and theequalization of the receiver.

Although a few embodiments of the present general inventive concept havebeen shown and described, it will be appreciated by those skilled in theart that changes may be made in these embodiments without departing fromthe principles and spirit of the general inventive concept, the scope ofwhich is defined in the appended claims and their equivalents.

1. A digital broadcast receiver comprising: a tuner to receive a datastream including known data; a demodulator to demodulate the datastream; and a known data detector to detect information about the knowndata from the demodulated data stream, and detecting the known dataaccording to the detected information; and an equalizer to equalize thedemodulated data stream using the known data, wherein the data stream istransmitted from a digital broadcast transmitter having a trellisencoder to perform trellis encoding using internal memories and to resetthe internal memories according to a control signal to control a trellisreset operation at a predetermined time point.
 2. The digital broadcastreceiver as claimed in claim 1, wherein the known data is included in apredetermined position of the data stream according to a control signalto control insertion of the known data in the digital broadcasttransmitter.
 3. The digital broadcast receiver as claimed in claim 1,wherein the data stream is a data stream of which Reed Solomon (RS)parity is compensated for corresponding to the memory reset in a RSencoder provided in the digital broadcast transmitter.
 4. The digitalbroadcast receiver as claimed in claim 1, wherein, if the known data isdetected, the demodulator demodulates a subsequent data stream using thedetected known data.
 5. The digital broadcast receiver as claimed inclaim 1, wherein the known data detector comprises: a symbol numberdetector to check a length of the known data inserted into the datastream and to determine a position and a number of a known symbolaccording to the coding of the known data; a segment generator togenerate at least one segment according to the position and the numberof the known symbol and generating a frame including the segment; anencoder to perform a coding process corresponding to a transmitting sideof the generated frame; and a known symbol output unit to insert thepredefined known data into the position corresponding to the knownsymbol of the encoded frame and outputting the frame.
 6. The digitalbroadcast receiver as claimed in claim 1, wherein the data stream is adata stream processed to have enhanced robustness.
 7. A streamprocessing method of a digital broadcast receiver, comprising: receivinga data stream including a known data; demodulating the data stream;detecting information about the known data from the demodulated datastream, and detecting the known data according to the detectedinformation; and equalizing the demodulated data stream using the knowndata, wherein the data stream is transmitted from a digital broadcasttransmitter having a trellis encoder for performing trellis encodingusing internal memories and resetting the internal memories according tothe control signal for controlling a trellis reset operation at apredetermined time point.
 8. The stream processing method as claimed inclaim 7, wherein the known data is included in a predetermined positionof the data stream according to a control signal for controllinginsertion of the known data in the digital broadcast transmitter.
 9. Thestream processing method as claimed in claim 7, wherein the data streamis a data stream of which Reed Solomon (RS) parity is compensated forcorresponding to the memory reset in a RS encoder provided in thedigital broadcast transmitter.
 10. The stream processing method asclaimed in claim 7, wherein the demodulating of the data streamcomprises demodulating the data stream using the detected known data.11. The stream processing method as claimed in claim 7, wherein thedetecting of the known data comprises: checking a length of the knowndata inserted into the data stream and determining a position and anumber of a known symbol according to the encoding of the known data;generating at least one segment according to the position and the numberof the known symbol and generating a frame including the segment;performing a coding process corresponding to a transmitting side of thegenerated frame; and inserting the predefined known data into theposition corresponding to the known symbol of the encoded frame andoutputting the frame.
 12. The stream processing method as claimed inclaim 7, wherein the data stream is a data stream processed to haveenhanced robustness.